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gaining time



 
 
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  #1  
Old January 8th 04, 03:16 PM
will
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Default gaining time

Hi Folks

I'm hopeing that somebody here can settle an argument for me and a
mate.

The days get longer and shorter during the year ,because of the earth
tilt to its axis...

Is the time gained or lost each day constant.. I reckon its got to be
something between 30 and 55 secondes of extra daylight (or darkness)
each day and that whatever the figure is it will always stay the
same... but my mate reckons that this figure increases as the longest
day approaches so for example its an extra minute of daylighht in
March but by June were getting twio extra minutes...

Any chance some body could settle this argument

cheers

Will
  #2  
Old January 8th 04, 04:53 PM
Martin Lewicki
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(will) wrote in
m:

Hi Folks

I'm hopeing that somebody here can settle an argument for me and a
mate.

The days get longer and shorter during the year ,because of the earth
tilt to its axis...

Is the time gained or lost each day constant.. I reckon its got to be
something between 30 and 55 secondes of extra daylight (or darkness)
each day and that whatever the figure is it will always stay the
same... but my mate reckons that this figure increases as the longest
day approaches so for example its an extra minute of daylighht in
March but by June were getting twio extra minutes...

Any chance some body could settle this argument

cheers

Will


The answer is not that simple.

The rate of change in length of the day is greatest at the March and
September equinoxes. The rate decreases to near zero at June and December
solstices.

The magnitude of the rate of change also deprends on your latitude. It is
minimum at the eqautor, increases in the temperate zones and becomes
extreme at the polar regions.

For example:

At 45° latitude
---------------
At March equinox (21 March)
the rate of change in length of day is 1m00s

At June solstice (21 June)
the rate of change in length of day is almost 0m02s


And near the polar regions.

At 60° latitude
---------------
At March equinox (21 March)
the rate of change in length of day is almost 2m59s

At June solstices (21June)
the rate of change in length of day is almost 0m10s

Martin Lewicki







  #3  
Old January 8th 04, 09:31 PM
OG
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Default


"will" wrote in message
m...
Hi Folks

I'm hopeing that somebody here can settle an argument for me and a
mate.

The days get longer and shorter during the year ,because of the earth
tilt to its axis...

Is the time gained or lost each day constant.. I reckon its got to be
something between 30 and 55 secondes of extra daylight (or darkness)
each day and that whatever the figure is it will always stay the
same... but my mate reckons that this figure increases as the longest
day approaches so for example its an extra minute of daylighht in
March but by June were getting twio extra minutes...

Any chance some body could settle this argument


Hi Will,
The main variation in the length of the day varies as a sine wave over the
year. The exact shape depends on your position on the earth's surface, but
it is a smooth curve as shown in
http://www.islandnet.com/~see/weathe...tos/sungrf.gif *

As you can see, the length of the day depends on the height of the graph;
but to measure the daily gain or loss you need to look at the _slope_ of the
graph.

As Martin has already said, the slope is steepest in March and September
(when the daylight time is closest to 12 hours exactly), I find the graph
helps to see why this is the case.

Hope this helps

Owen

*the graph shows length of day, and also the amount of sunlight energy
falling per day; summer's sunlight is brighter, so the insolation curve is
'pointier'.


  #4  
Old January 9th 04, 12:20 AM
eyelessgame
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Default

(will) wrote in message om...
Hi Folks

I'm hopeing that somebody here can settle an argument for me and a
mate.

The days get longer and shorter during the year ,because of the earth
tilt to its axis...

Is the time gained or lost each day constant.. I reckon its got to be
something between 30 and 55 secondes of extra daylight (or darkness)
each day and that whatever the figure is it will always stay the
same... but my mate reckons that this figure increases as the longest
day approaches so for example its an extra minute of daylighht in
March but by June were getting twio extra minutes...

Any chance some body could settle this argument


Gosh, if only there were some resource you could consult where you
could settle this for yourself.

Maybe, if we hooked a whole bunch of computers together, and let them
talk to each other, somebody might write a computer program that could
calculate sunrise and sunset times!

But then we'd have the problem of *finding* that information. Hey, I
have a really cool idea. Suppose someone were to write a computer
program that would go out and look for everything that any of those
computers made public, and then we could make it so anybody could go
to that computer program, and type in what they were searching for,
and it would show up *right on their own computer*!

Nah. Too farfetched.

http://aa.usno.navy.mil/data/docs/RS_OneYear.html

From this location, it's really easy to see that close to the
solstices, the rise and set times vary hardly at all, whereas three
months apart from those times at the equinoxes, we gain/lose more than
two minutes every day.
  #5  
Old January 9th 04, 01:11 AM
CeeBee
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Default

(will) wrote in alt.astronomy:


Any chance some body could settle this argument



http://www.rfleet.clara.net/graphdark/download.htm

can show you who's right. Nifty program.

--
CeeBee


"I am not a crook"

  #7  
Old January 9th 04, 02:22 AM
will
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Posts: n/a
Default

Looks like we were both wrong.. ho hum thanks for sorting it out..

Martin Lewicki wrote in message ...
(will) wrote in
m:

Hi Folks

I'm hopeing that somebody here can settle an argument for me and a
mate.

The days get longer and shorter during the year ,because of the earth
tilt to its axis...

Is the time gained or lost each day constant.. I reckon its got to be
something between 30 and 55 secondes of extra daylight (or darkness)
each day and that whatever the figure is it will always stay the
same... but my mate reckons that this figure increases as the longest
day approaches so for example its an extra minute of daylighht in
March but by June were getting twio extra minutes...

Any chance some body could settle this argument

cheers

Will


The answer is not that simple.

The rate of change in length of the day is greatest at the March and
September equinoxes. The rate decreases to near zero at June and December
solstices.

The magnitude of the rate of change also deprends on your latitude. It is
minimum at the eqautor, increases in the temperate zones and becomes
extreme at the polar regions.

For example:

At 45° latitude
---------------
At March equinox (21 March)
the rate of change in length of day is 1m00s

At June solstice (21 June)
the rate of change in length of day is almost 0m02s


And near the polar regions.

At 60° latitude
---------------
At March equinox (21 March)
the rate of change in length of day is almost 2m59s

At June solstices (21June)
the rate of change in length of day is almost 0m10s

Martin Lewicki

  #8  
Old January 9th 04, 03:41 PM
BillP
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Posts: n/a
Default


"will" wrote in message
m...
Hi Folks

I'm hopeing that somebody here can settle an argument for me and a
mate.

The days get longer and shorter during the year ,because of the earth
tilt to its axis...

Is the time gained or lost each day constant.. I reckon its got to be
something between 30 and 55 secondes of extra daylight (or darkness)
each day and that whatever the figure is it will always stay the
same... but my mate reckons that this figure increases as the longest
day approaches so for example its an extra minute of daylighht in
March but by June were getting twio extra minutes...

Any chance some body could settle this argument

cheers

Will


Hi Will,

I thought about this a couple of years ago. I guessed that the sunrise times
would closely follow a sign wave, and wanted to see if it was right. The
only tool I'd got was SKYGLOBE. I noted sunrise times for each week and
plotted the results on a graph.
The result is on
http://www.geocities.com/wjp_gof/sunrise.doc








 




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